﻿using System;
using System.Collections.Generic;
using System.Web;
using System.Web.UI;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.IO;
using System.Drawing.Imaging;

namespace dooll.Passport
{
    /// <summary>
    /// 验证码图片
    /// </summary>
    public partial class ValidCode : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            Response.CacheControl = "no-cache";
            CreateCheckCodeImage(GenerateCheckCode());
        }

        #region 生成4位随机数
        private string GenerateCheckCode()
        {
            int number;
            char code;
            string checkCode = String.Empty;
            threadSafeRandom random = new threadSafeRandom();
            for (int i = 0; i < 4; i++)
            {
                number = random.Next();

                //if (number % 2 == 0)
                //{
                //    code = (char)('0' + (char)(number % 10));
                //}
                //else
                //{
                //    code = (char)('A' + (char)(number % 26));
                //}

                code = (char)('0' + (char)(number % 10));

                checkCode += code.ToString();
            }

            HttpCookie checkcodeCookie = new HttpCookie("CheckCode", checkCode);
            checkcodeCookie.Path = "/";
            //checkcodeCookie.HttpOnly = false;
            Response.Cookies.Add(checkcodeCookie);

            //HttpContext.Current.Session["CheckCode"] = checkCode;
            return checkCode;
        }
        #endregion

        #region 生成验证码图片
        private void CreateCheckCodeImage(string checkCode)
        {
            if (checkCode == null || checkCode.Trim() == String.Empty)
            {
                return;
            }
            Bitmap image = new Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 18);
            Graphics g = Graphics.FromImage(image);
            try
            {
                //生成随机生成器
                Random random = new Random();

                //清空图片背景色
                g.Clear(Color.White);

                //画图片的背景噪音线
                for (int i = 0; i < 25; i++)
                {
                    int x1 = random.Next(image.Width);
                    int x2 = random.Next(image.Width);
                    int y1 = random.Next(image.Height);
                    int y2 = random.Next(image.Height);

                    g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
                }

                Font font = new Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));
                LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.DarkBlue, Color.DarkRed, 1.7f, true);
                g.DrawString(checkCode, font, brush, 2, 1);

                //画图片的前景噪音点
                for (int i = 0; i < 100; i++)
                {
                    int x = random.Next(image.Width);
                    int y = random.Next(image.Height);

                    image.SetPixel(x, y, Color.FromArgb(random.Next()));
                }

                //画图片的边框线
                g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
                MemoryStream ms = new MemoryStream();
                image.Save(ms, ImageFormat.Gif);
                Response.ClearContent();
                Response.ContentType = "image/Gif";
                Response.BinaryWrite(ms.ToArray());
            }
            finally
            {
                g.Dispose();
                image.Dispose();
            }
        }
        #endregion
    }

    /// <summary>
    /// 线程保护的随机数
    /// </summary>
    public class threadSafeRandom
    {
        private Random rd = new Random();
        public int Next(){
            lock (rd)
            {
                return rd.Next();
            }
        }
    }
}
